1. Field of the Invention
The invention relates to a process for preparing cyanoacetamide by esterification without additional catalyst. During this esterification crude cyanoacetic acid is reacted with a monohydric alcohol which forms an azeotrope with water. The resulting ester is reacted with ammonia in the presence of a basic catalyst to give cyanoacetamide, followed by work-up using a mechanical separating operation and thermal treatment.
2. Discussion of the Background
Cyanoacetamide is an important intermediate for preparing drugs and pharmaceutical products. It is used inter alia for preparing malononitrile.
Syntheses of cyanoacetamide from cyanoacetic esters are known from the literature. For example, Organic Synthesis Collect., Volume 1, pg. 179 describes a process in which ethyl cyanoacetate is reacted with concentrated aqueous ammonia. This results in wastewater which is polluted with organic products and which must be disposed of. Moreover, it is necessary to work up the mother liquor to achieve a good yield. Processes of this type are complicated and not economic.
European Patent Application EP-A-0 583 694 describes the use of butanol in a large excess of 5 to 30 times the molar amount of cyanoacetic acid and a strongly acidic catalyst for the esterification. The esterification times are very long despite the catalyst. (For example, a reaction time of 13 hours is disclosed in the Examples of EP-A-0 583 694.